GAUGE-INDEPENDENT ANALYSIS OF K-L-]E-MU IN LEFT-RIGHT MODELS

The lepton-flavour-violating decay K-L --> e mu is studied in detail w ithin the context of SU(2)(R)xSU(2)(L)xU(1)((B-L)) models, which inclu de heavy Majorana neutrinos. Particular attention is paid to the gauge independence of this decay process to one loop. In analogy with earli er studies on the K-0<(K)over bar (0)> mixing, it is explicitly shown how restoration of gauge invariance occurs in the decay amplitude cont aining the box diagrams, when the relevant Higgs-dependent self-energy and vertex graphs are taken into account in the on-shell skeleton ren ormalization scheme. Based on the analytic expressions so derived, we find that the branching ratio B(K-L --> e mu) can be considerably enha nced due to the presence of left-and right-handed currents in the loop , and can reach values close to or even larger than the present experi mental limit 3.3 x 10(-11) in the manifest left-right symmetric model. Constraints on the parameter space of typical left-right models are d erived from the possible decay K-L --> e mu and a global analysis of o ther low-energy data. (C) 1998 Elsevier Science B.V.